Plume collimation for laser ablation electrospray ionization mass spectrometry

Abstract

In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

What is claimed is: 
     
       1. A device comprising transmission geometry, the device comprising:
 a capillary including a first end and a second end; 
 a pulsed, mid-infrared laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; 
 an electrospray apparatus to generate an electrospray plume to intercept the ablation plume exiting the capillary to produce ions; and 
 a mass spectrometer having an ion transfer inlet to capture the ions, 
 wherein the mid-infrared laser is on a first side of the sample and at least a portion of the ablation plume is generated on a second side of the sample. 
 
     
     
       2. The device of  claim 1 , wherein the plume is a collimated ablation plume. 
     
     
       3. The device of  claim 1 , wherein the ablation plume is not a freely expanding ablation plume. 
     
     
       4. The device of  claim 1 , wherein the second end of the capillary comprises an open end and the electrospray apparatus comprises an electrospray emitter tip, and an angle between the open end of the capillary and the electrospray emitter tip is about 90°. 
     
     
       5. The device of  claim 1 , wherein the capillary comprises an inner diameter from 0.1 mm to 5 mm and a length from 1 mm to 5 mm. 
     
     
       6. The device of  claim 1 , wherein the capillary comprises a chemically modified interior surface. 
     
     
       7. The device of  claim 1  comprising at least one of focusing optics, an optical fiber, and a hollow waveguide to couple the energy to the sample in the capillary and deliver the energy to the sample. 
     
     
       8. The device of  claim 1 , wherein the optical fiber comprises a linearly tapered tip. 
     
     
       9. The device of  claim 1 , wherein a portion of the optical fiber is positioned inside the capillary and the sample is positioned inside the capillary intermediate the optical fiber and the second end of the capillary. 
     
     
       10. The device of  claim 1 , wherein the capillary comprises a hollow waveguide. 
     
     
       11. The device of  claim 1 , wherein the sample comprises water and the energy is absorbed by the water in the sample, and wherein the sample is not under vacuum. 
     
     
       12. The device of  claim 1 , wherein the sample comprises a suspension of at least one cell in an aqueous solution and a sample volume from  1  picoliter to 2 microliters. 
     
     
       13. The device of  claim 1  comprising a flow cytometer in fluid communication with the capillary. 
     
     
       14. The device of  claim 1  comprising:
 a flow through capillary to hydrodynamically focus the sample in a stream of fluid; 
 a continuous laser on a first side of the flow through capillary to irradiate the stream of fluid with a focused beam, wherein the focused beam is upstream from the mid-infrared laser; 
 a detector on a second side of the flow through capillary to detect when the sample passes the focused beam; and 
 a delay generator to activate the mid-infrared laser when the sample is at a point of ablation in the capillary, wherein the delay generator is in electrical communication with the detector and the mid-infrared laser. 
 
     
     
       15. A method comprising:
 ablating a sample by a mid-infrared laser pulse in a capillary to generate an ablation plume in the capillary; ejecting at least a portion of the ablation plume from the capillary on a side of the sample opposite from the mid-infrared laser; 
 intercepting the ablation plume by an electrospray plume after it exits from the capillary to produce ions; and 
 detecting the ions by mass spectrometry; 
 wherein the ablation plume is a collimated ablation plume; and 
 wherein the sample comprises water and the laser energy is absorbed by the water in the sample. 
 
     
     
       16. The method of  claim 15  comprising collimating the ablation plume with one of the capillary and a hollow waveguide to generate the collimated ablation plume. 
     
     
       17. The method of  claim 15  comprising ablating the sample in a hollow waveguide. 
     
     
       18. The method of  claim 15  comprising:
 hydrodynamically focusing the sample in a stream of fluid by one of a flow cytometer and a flow through capillary; 
 irradiating the stream of fluid with a focused beam from a continuous laser; 
 detecting when the sample passes the focused beam; and 
 activating the mid-infrared laser when the sample is at a point of ablation in the capillary to ablate the sample.